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Stabilise inline_const #104087

Merged
merged 5 commits into from
Apr 24, 2024
Merged

Stabilise inline_const #104087

merged 5 commits into from
Apr 24, 2024

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nbdd0121
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@nbdd0121 nbdd0121 commented Nov 7, 2022

Stabilisation Report

Summary

This PR will stabilise inline_const feature in expression position. inline_const_pat is still unstable and will not be stabilised.

The feature will allow code like this:

foo(const { 1 + 1 })

which is roughly desugared into

struct Foo;
impl Foo {
    const FOO: i32 = 1 + 1;
}
foo(Foo::FOO)

This feature is from rust-lang/rfcs#2920 and is tracked in #76001 (the tracking issue should not be closed as it needs to track inline const in pattern position). The initial implementation is done in #77124.

Difference from RFC

There are two major differences (enhancements) as implemented from the RFC. First thing is that the RFC says that the type of an inline const block inferred from the content within it, but we currently can infer the type using the information from outside the const block as well. This is a frequently requested feature to the initial implementation (e.g. #89964). The inference is implemented in #89561 and is done by treating inline const similar to a closure and therefore share inference context with its parent body.

This allows code like:

let v: Vec<i32> = const { Vec::new() };

Another enhancement that differs from the RFC is that we currently allow inline consts to reference generic parameters. This is implemented in #96557.

This allows code like:

fn create_none_array<T, const N: usize>() -> [Option<T>; N] {
    [const { None::<T> }; N]
}

This enhancement also makes inline const usable as static asserts:

fn require_zst<T>() {
    const { assert!(std::mem::size_of::<T>() == 0) }
}

Documentation

Reference: rust-lang/reference#1295

Unresolved issues

We still have a few issues that are not resolved, but I don't think it necessarily has to block stabilisation:

Tests

There are a few tests in https://github.com/rust-lang/rust/tree/master/src/test/ui/inline-const

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rustbot commented Nov 7, 2022

r? @JohnTitor

(rustbot has picked a reviewer for you, use r? to override)

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Nov 7, 2022
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rustbot commented Nov 7, 2022

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

  • Stabilizing library features
  • Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
  • Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
  • Changing public documentation in ways that create new stability guarantees
  • Changing observable runtime behavior of library APIs

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@JohnTitor JohnTitor added the needs-fcp This change is insta-stable, so needs a completed FCP to proceed. label Nov 7, 2022
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I think this needs FCP, cc @rust-lang/lang

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nbdd0121 commented Nov 15, 2022

@rustbot label: -T-libs +T-lang +I-lang-nominated

@rustbot rustbot added I-lang-nominated Nominated for discussion during a lang team meeting. T-lang Relevant to the language team, which will review and decide on the PR/issue. and removed T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Nov 15, 2022
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@rfcbot rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Nov 15, 2022
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@rfcbot rfcbot removed proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Nov 15, 2022
@scottmcm scottmcm removed the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Nov 15, 2022
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scottmcm commented Nov 15, 2022

Thanks for the report! It looks like the current state is enough to allow this to work:

pub fn create_none_array<T, const N: usize>() -> [Option<T>; N] {
    [const { None }; N]
}

which is the use that keeps coming up on URLO. And this also keeps coming up (1 2) on IRLO as needed (or at least wanted) for various things.

So let's do it!

@rfcbot fcp merge

cc Tracking Issue #76001, which also covers patterns so isn't closed by this PR.

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@rfcbot rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Nov 15, 2022
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(Sorry, compiler folks. One day I'll remember to check the labels before kicking off an FCP.)

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Finished benchmarking commit (7bb4f08): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

This benchmark run did not return any relevant results for this metric.

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

mean range count
Regressions ❌
(primary)
- - 0
Regressions ❌
(secondary)
- - 0
Improvements ✅
(primary)
-2.0% [-2.0%, -2.0%] 1
Improvements ✅
(secondary)
-2.9% [-3.3%, -2.5%] 3
All ❌✅ (primary) -2.0% [-2.0%, -2.0%] 1

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 674.062s -> 672.117s (-0.29%)
Artifact size: 316.12 MiB -> 316.14 MiB (0.01%)

@joshlf joshlf mentioned this pull request Apr 24, 2024
42 tasks
@nbdd0121 nbdd0121 deleted the const branch April 24, 2024 23:02
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@rustbot label +relnotes

@rustbot rustbot added the relnotes Marks issues that should be documented in the release notes of the next release. label Apr 29, 2024
@apiraino apiraino removed the to-announce Announce this issue on triage meeting label Apr 29, 2024
fmease added a commit to fmease/rust that referenced this pull request Jun 4, 2024
…trieb

Use inline const blocks to create arrays of `MaybeUninit`.

This PR contains 2 changes enabled by the fact that [`inline_const` is now stable](rust-lang#104087), and was split out of rust-lang#125082.

1. Use inline const instead of `unsafe` to construct arrays in `MaybeUninit` examples.

   Rationale: Demonstrate good practice of avoiding `unsafe` code where it is not strictly necessary.

4. Use inline const instead of `unsafe` to implement `MaybeUninit::uninit_array()`.

    This is arguably giving the compiler more work to do, in exchange for eliminating just one single internal unsafe block, so it's less certain that this is good on net.

r​? `@Nilstrieb`
workingjubilee added a commit to workingjubilee/rustc that referenced this pull request Jun 5, 2024
…trieb

Use inline const blocks to create arrays of `MaybeUninit`.

This PR contains 2 changes enabled by the fact that [`inline_const` is now stable](rust-lang#104087), and was split out of rust-lang#125082.

1. Use inline const instead of `unsafe` to construct arrays in `MaybeUninit` examples.

   Rationale: Demonstrate good practice of avoiding `unsafe` code where it is not strictly necessary.

4. Use inline const instead of `unsafe` to implement `MaybeUninit::uninit_array()`.

    This is arguably giving the compiler more work to do, in exchange for eliminating just one single internal unsafe block, so it's less certain that this is good on net.

r​? `@Nilstrieb`
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Jun 5, 2024
Rollup merge of rust-lang#125995 - kpreid:const-uninit-stable, r=Nilstrieb

Use inline const blocks to create arrays of `MaybeUninit`.

This PR contains 2 changes enabled by the fact that [`inline_const` is now stable](rust-lang#104087), and was split out of rust-lang#125082.

1. Use inline const instead of `unsafe` to construct arrays in `MaybeUninit` examples.

   Rationale: Demonstrate good practice of avoiding `unsafe` code where it is not strictly necessary.

4. Use inline const instead of `unsafe` to implement `MaybeUninit::uninit_array()`.

    This is arguably giving the compiler more work to do, in exchange for eliminating just one single internal unsafe block, so it's less certain that this is good on net.

r​? `@Nilstrieb`
flip1995 pushed a commit to flip1995/rust-clippy that referenced this pull request Jun 28, 2024
Use inline const blocks to create arrays of `MaybeUninit`.

This PR contains 2 changes enabled by the fact that [`inline_const` is now stable](rust-lang/rust#104087), and was split out of #125082.

1. Use inline const instead of `unsafe` to construct arrays in `MaybeUninit` examples.

   Rationale: Demonstrate good practice of avoiding `unsafe` code where it is not strictly necessary.

4. Use inline const instead of `unsafe` to implement `MaybeUninit::uninit_array()`.

    This is arguably giving the compiler more work to do, in exchange for eliminating just one single internal unsafe block, so it's less certain that this is good on net.

r​? `@Nilstrieb`
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Oct 13, 2024
This is based on the pkgsrc-wip rust180 package, retaining
the main pkgsrc changes as best as I could.

Pkgsrc changes:
 * Adapt checksums and patches.
 * Make this work again on big-endian aarch64 (at least on NetBSD).
 * Make the choice of GCC = 12 work for sparc64 by testing options
   after options.mk is included (which is required...).  Makes this
   work on NetBSD/sparc64 10.0 again.

Upstream chnages:

Version 1.80.1 (2024-08-08)
===========================

- [Fix miscompilation in the jump threading MIR optimization when
  comparing floats]
  (rust-lang/rust#128271)
- [Revert changes to the `dead_code` lint from 1.80.0]
  (rust-lang/rust#128618)

Version 1.80.0 (2024-07-25)
==========================

Language
--------
- [Document maximum allocation size]
  (rust-lang/rust#116675)
- [Allow zero-byte offsets and ZST read/writes on arbitrary pointers]
  (rust-lang/rust#117329)
- [Support C23's variadics without a named parameter]
  (rust-lang/rust#124048)
- [Stabilize `exclusive_range_pattern` feature]
  (rust-lang/rust#124459)
- [Guarantee layout and ABI of `Result` in some scenarios]
  (rust-lang/rust#124870)

Compiler
--------
- [Update cc crate to v1.0.97 allowing additional spectre mitigations
  on MSVC targets]
  (rust-lang/rust#124892)
- [Allow field reordering on types marked `repr(packed(1))`]
  (rust-lang/rust#125360)
- [Add a lint against never type fallback affecting unsafe code]
  (rust-lang/rust#123939)
- [Disallow cast with trailing braced macro in let-else]
  (rust-lang/rust#125049)
- [Expand `for_loops_over_fallibles` lint to lint on fallibles
  behind references.]
  (rust-lang/rust#125156)
- [self-contained linker: retry linking without `-fuse-ld=lld` on
  CCs that don't support it]
  (rust-lang/rust#125417)
- [Do not parse CVarArgs (`...`) as a type in trait bounds]
  (rust-lang/rust#125863)
- Improvements to LLDB formatting [#124458]
  (rust-lang/rust#124458) [#124500]
  (rust-lang/rust#124500)
- [For the wasm32-wasip2 target default to PIC and do not use `-fuse-ld=lld`]
  (rust-lang/rust#124858)
- [Add x86_64-unknown-linux-none as a tier 3 target]
  (rust-lang/rust#125023)
- [Lint on `foo.into_iter()` resolving to `&Box<[T]>: IntoIterator`]
  (rust-lang/rust#124097)

Libraries
---------
- [Add `size_of` and `size_of_val` and `align_of` and `align_of_val`
  to the prelude]
  (rust-lang/rust#123168)
- [Abort a process when FD ownership is violated]
  (rust-lang/rust#124210)
- [io::Write::write_fmt: panic if the formatter fails when the
  stream does not fail]
  (rust-lang/rust#125012)
- [Panic if `PathBuf::set_extension` would add a path separator]
  (rust-lang/rust#125070)
- [Add assert_unsafe_precondition to unchecked_{add,sub,neg,mul,shl,shr}
  methods] (rust-lang/rust#121571)
- [Update `c_char` on AIX to use the correct type]
  (rust-lang/rust#122986)
- [`offset_of!` no longer returns a temporary]
  (rust-lang/rust#124484)
- [Handle sigma in `str.to_lowercase` correctly]
  (rust-lang/rust#124773)
- [Raise `DEFAULT_MIN_STACK_SIZE` to at least 64KiB]
  (rust-lang/rust#126059)

Stabilized APIs
---------------
- [`impl Default for Rc<CStr>`]
  (https://doc.rust-lang.org/beta/alloc/rc/struct.Rc.html#impl-Default-for-Rc%3CCStr%3E)
- [`impl Default for Rc<str>`]
  (https://doc.rust-lang.org/beta/alloc/rc/struct.Rc.html#impl-Default-for-Rc%3Cstr%3E)
- [`impl Default for Rc<[T]>`]
  (https://doc.rust-lang.org/beta/alloc/rc/struct.Rc.html#impl-Default-for-Rc%3C%5BT%5D%3E)
- [`impl Default for Arc<str>`]
  (https://doc.rust-lang.org/beta/alloc/sync/struct.Arc.html#impl-Default-for-Arc%3Cstr%3E)
- [`impl Default for Arc<CStr>`]
  (https://doc.rust-lang.org/beta/alloc/sync/struct.Arc.html#impl-Default-for-Arc%3CCStr%3E)
- [`impl Default for Arc<[T]>`]
  (https://doc.rust-lang.org/beta/alloc/sync/struct.Arc.html#impl-Default-for-Arc%3C%5BT%5D%3E)
- [`impl IntoIterator for Box<[T]>`]
  (https://doc.rust-lang.org/beta/alloc/boxed/struct.Box.html#impl-IntoIterator-for-Box%3C%5BI%5D,+A%3E)
- [`impl FromIterator<String> for Box<str>`]
  (https://doc.rust-lang.org/beta/alloc/boxed/struct.Box.html#impl-FromIterator%3CString%3E-for-Box%3Cstr%3E)
- [`impl FromIterator<char> for Box<str>`]
  (https://doc.rust-lang.org/beta/alloc/boxed/struct.Box.html#impl-FromIterator%3Cchar%3E-for-Box%3Cstr%3E)
- [`LazyCell`]
  (https://doc.rust-lang.org/beta/core/cell/struct.LazyCell.html)
- [`LazyLock`]
  (https://doc.rust-lang.org/beta/std/sync/struct.LazyLock.html)
- [`Duration::div_duration_f32`]
  (https://doc.rust-lang.org/beta/std/time/struct.Duration.html#method.div_duration_f32)
- [`Duration::div_duration_f64`]
  (https://doc.rust-lang.org/beta/std/time/struct.Duration.html#method.div_duration_f64)
- [`Option::take_if`]
  (https://doc.rust-lang.org/beta/std/option/enum.Option.html#method.take_if)
- [`Seek::seek_relative`]
  (https://doc.rust-lang.org/beta/std/io/trait.Seek.html#method.seek_relative)
- [`BinaryHeap::as_slice`]
  (https://doc.rust-lang.org/beta/std/collections/struct.BinaryHeap.html#method.as_slice)
- [`NonNull::offset`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.offset)
- [`NonNull::byte_offset`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_offset)
- [`NonNull::add`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.add)
- [`NonNull::byte_add`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_add)
- [`NonNull::sub`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.sub)
- [`NonNull::byte_sub`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_sub)
- [`NonNull::offset_from`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.offset_from)
- [`NonNull::byte_offset_from`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_offset_from)
- [`NonNull::read`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.read)
- [`NonNull::read_volatile`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.read_volatile)
- [`NonNull::read_unaligned`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.read_unaligned)
- [`NonNull::write`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write)
- [`NonNull::write_volatile`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write_volatile)
- [`NonNull::write_unaligned`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write_unaligned)
- [`NonNull::write_bytes`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write_bytes)
- [`NonNull::copy_to`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_to)
- [`NonNull::copy_to_nonoverlapping`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_to_nonoverlapping)
- [`NonNull::copy_from`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_from)
- [`NonNull::copy_from_nonoverlapping`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_from_nonoverlapping)
- [`NonNull::replace`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.replace)
- [`NonNull::swap`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.swap)
- [`NonNull::drop_in_place`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.drop_in_place)
- [`NonNull::align_offset`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.align_offset)
- [`<[T]>::split_at_checked`]
  (https://doc.rust-lang.org/beta/std/primitive.slice.html#method.split_at_checked)
- [`<[T]>::split_at_mut_checked`]
  (https://doc.rust-lang.org/beta/std/primitive.slice.html#method.split_at_mut_checked)
- [`str::split_at_checked`]
  (https://doc.rust-lang.org/beta/std/primitive.str.html#method.split_at_checked)
- [`str::split_at_mut_checked`]
  (https://doc.rust-lang.org/beta/std/primitive.str.html#method.split_at_mut_checked)
- [`str::trim_ascii`]
  (https://doc.rust-lang.org/beta/std/primitive.str.html#method.trim_ascii)
- [`str::trim_ascii_start`]
  (https://doc.rust-lang.org/beta/std/primitive.str.html#method.trim_ascii_start)
- [`str::trim_ascii_end`]
  (https://doc.rust-lang.org/beta/std/primitive.str.html#method.trim_ascii_end)
- [`<[u8]>::trim_ascii`]
  (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.trim_ascii)
- [`<[u8]>::trim_ascii_start`]
  (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.trim_ascii_start)
- [`<[u8]>::trim_ascii_end`]
  (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.trim_ascii_end)
- [`Ipv4Addr::BITS`]
  (https://doc.rust-lang.org/beta/core/net/struct.Ipv4Addr.html#associatedconstant.BITS)
- [`Ipv4Addr::to_bits`]
  (https://doc.rust-lang.org/beta/core/net/struct.Ipv4Addr.html#method.to_bits)
- [`Ipv4Addr::from_bits`]
  (https://doc.rust-lang.org/beta/core/net/struct.Ipv4Addr.html#method.from_bits)
- [`Ipv6Addr::BITS`]
  (https://doc.rust-lang.org/beta/core/net/struct.Ipv6Addr.html#associatedconstant.BITS)
- [`Ipv6Addr::to_bits`]
  (https://doc.rust-lang.org/beta/core/net/struct.Ipv6Addr.html#method.to_bits)
- [`Ipv6Addr::from_bits`]
  (https://doc.rust-lang.org/beta/core/net/struct.Ipv6Addr.html#method.from_bits)
- [`Vec::<[T; N]>::into_flattened`]
  (https://doc.rust-lang.org/beta/alloc/vec/struct.Vec.html#method.into_flattened)
- [`<[[T; N]]>::as_flattened`]
  (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.as_flattened)
- [`<[[T; N]]>::as_flattened_mut`]
  (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.as_flattened_mut)

These APIs are now stable in const contexts:

- [`<[T]>::last_chunk`]
  (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.last_chunk)
- [`BinaryHeap::new`]
  (https://doc.rust-lang.org/beta/std/collections/struct.BinaryHeap.html#method.new)

Cargo
-----

- [Stabilize `-Zcheck-cfg` as always enabled]
  (rust-lang/cargo#13571)
- [Warn, rather than fail publish, if a target is excluded]
  (rust-lang/cargo#13713)
- [Add special `check-cfg` lint config for the `unexpected_cfgs` lint]
  (rust-lang/cargo#13913)
- [Stabilize `cargo update --precise <yanked>`]
  (rust-lang/cargo#13974)
- [Don't change file permissions on `Cargo.toml` when using `cargo add`]
  (rust-lang/cargo#13898)
- [Support using `cargo fix` on IPv6-only networks]
  (rust-lang/cargo#13907)

Rustdoc
-----

- [Allow searching for references]
  (rust-lang/rust#124148)
- [Stabilize `custom_code_classes_in_docs` feature]
  (rust-lang/rust#124577)
- [fix: In cross-crate scenarios show enum variants on type aliases of enums]
  (rust-lang/rust#125300)

Compatibility Notes
-------------------

- [rustfmt estimates line lengths differently when using non-ascii characters]
  (rust-lang/rustfmt#6203)
- [Type aliases are now handled correctly in orphan check]
  (rust-lang/rust#117164)
- [Allow instructing rustdoc to read from stdin via `-`]
  (rust-lang/rust#124611)
- [`std::env::{set_var, remove_var}` can no longer be converted to
  safe function pointers and no longer implement the `Fn` family of
  traits]
  (rust-lang/rust#124636)
- [Warn (or error) when `Self` constructor from outer item is
  referenced in inner nested item]
  (rust-lang/rust#124187)
- [Turn `indirect_structural_match` and `pointer_structural_match`
  lints into hard errors]
  (rust-lang/rust#124661)
- [Make `where_clause_object_safety` lint a regular object safety violation]
  (rust-lang/rust#125380)
- [Turn `proc_macro_back_compat` lint into a hard error.]
  (rust-lang/rust#125596)
- [Detect unused structs even when implementing private traits]
  (rust-lang/rust#122382)
- [`std::sync::ReentrantLockGuard<T>` is no longer `Sync` if `T: !Sync`]
  (rust-lang/rust#125527) which means
  [`std::io::StdoutLock` and `std::io::StderrLock` are no longer
  Sync] (rust-lang/rust#127340)

Internal Changes
----------------

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

- Misc improvements to size of generated html by rustdoc e.g. [#124738]
  (rust-lang/rust#124738) and [#123734]
  (rust-lang/rust#123734)
- [MSVC targets no longer depend on libc]
  (rust-lang/rust#124050)


Version 1.79.0 (2024-06-13)
==========================

Language
--------
- [Stabilize inline `const {}` expressions.]
  (rust-lang/rust#104087)
- [Prevent opaque types being instantiated twice with different
  regions within the same function.]
  (rust-lang/rust#116935)
- [Stabilize WebAssembly target features that are in phase 4 and 5.]
  (rust-lang/rust#117457)
- [Add the `redundant_lifetimes` lint to detect lifetimes which
  are semantically redundant.]
  (rust-lang/rust#118391)
- [Stabilize the `unnameable_types` lint for public types that can't be named.]
  (rust-lang/rust#120144)
- [Enable debuginfo in macros, and stabilize `-C collapse-macro-debuginfo`
  and `#[collapse_debuginfo]`.]
  (rust-lang/rust#120845)
- [Propagate temporary lifetime extension into `if` and `match` expressions.]
  (rust-lang/rust#121346)
- [Restrict promotion of `const fn` calls.]
  (rust-lang/rust#121557)
- [Warn against refining impls of crate-private traits with
  `refining_impl_trait` lint.]
  (rust-lang/rust#121720)
- [Stabilize associated type bounds (RFC 2289).]
  (rust-lang/rust#122055)
- [Stabilize importing `main` from other modules or crates.]
  (rust-lang/rust#122060)
- [Check return types of function types for well-formedness]
  (rust-lang/rust#115538)
- [Rework `impl Trait` lifetime inference]
  (rust-lang/rust#116891)
- [Change inductive trait solver cycles to be ambiguous]
  (rust-lang/rust#122791)

Compiler
--------
- [Define `-C strip` to only affect binaries, not artifacts like `.pdb`.]
  (rust-lang/rust#115120)
- [Stabilize `-Crelro-level` for controlling runtime link hardening.]
  (rust-lang/rust#121694)
- [Stabilize checking of `cfg` names and values at compile-time
  with `--check-cfg`.]
  (rust-lang/rust#123501)
  *Note that this only stabilizes the compiler part, the Cargo part
  is still unstable in this release.*
- [Add `aarch64-apple-visionos` and `aarch64-apple-visionos-sim`
  tier 3 targets.]
  (rust-lang/rust#121419)
- [Add `riscv32ima-unknown-none-elf` tier 3 target.]
  (rust-lang/rust#122696)
- [Promote several Windows targets to tier 2]
  (rust-lang/rust#121712):
  `aarch64-pc-windows-gnullvm`, `i686-pc-windows-gnullvm`, and
  `x86_64-pc-windows-gnullvm`.

Refer to Rust's [platform support page][platform-support-doc]
for more information on Rust's tiered platform support.

Libraries
---------

- [Implement `FromIterator` for `(impl Default + Extend, impl
  Default + Extend)`.]
  (rust-lang/rust#107462)
- [Implement `{Div,Rem}Assign<NonZero<X>>` on `X`.]
  (rust-lang/rust#121952)
- [Document overrides of `clone_from()` in core/std.]
  (rust-lang/rust#122201)
- [Link MSVC default lib in core.]
  (rust-lang/rust#122268)
- [Caution against using `transmute` between pointers and integers.]
  (rust-lang/rust#122379)
- [Enable frame pointers for the standard library.]
  (rust-lang/rust#122646)

Stabilized APIs
---------------

- [`{integer}::unchecked_add`]
  (https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_add)
- [`{integer}::unchecked_mul`]
  (https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_mul)
- [`{integer}::unchecked_sub`]
  (https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_sub)
- [`<[T]>::split_at_unchecked`]
  (https://doc.rust-lang.org/stable/core/primitive.slice.html#method.split_at_unchecked)
- [`<[T]>::split_at_mut_unchecked`]
  (https://doc.rust-lang.org/stable/core/primitive.slice.html#method.split_at_mut_unchecked)
- [`<[u8]>::utf8_chunks`]
  (https://doc.rust-lang.org/stable/core/primitive.slice.html#method.utf8_chunks)
- [`str::Utf8Chunks`]
  (https://doc.rust-lang.org/stable/core/str/struct.Utf8Chunks.html)
- [`str::Utf8Chunk`]
  (https://doc.rust-lang.org/stable/core/str/struct.Utf8Chunk.html)
- [`<*const T>::is_aligned`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_aligned)
- [`<*mut T>::is_aligned`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_aligned-1)
- [`NonNull::is_aligned`]
  (https://doc.rust-lang.org/stable/core/ptr/struct.NonNull.html#method.is_aligned)
- [`<*const [T]>::len`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.len)
- [`<*mut [T]>::len`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.len-1)
- [`<*const [T]>::is_empty`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_empty)
- [`<*mut [T]>::is_empty`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_empty-1)
- [`NonNull::<[T]>::is_empty`]
  (https://doc.rust-lang.org/stable/core/ptr/struct.NonNull.html#method.is_empty)
- [`CStr::count_bytes`]
  (https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.count_bytes)
- [`io::Error::downcast`]
  (https://doc.rust-lang.org/stable/std/io/struct.Error.html#method.downcast)
- [`num::NonZero<T>`]
  (https://doc.rust-lang.org/stable/core/num/struct.NonZero.html)
- [`path::absolute`]
  (https://doc.rust-lang.org/stable/std/path/fn.absolute.html)
- [`proc_macro::Literal::byte_character`]
  (https://doc.rust-lang.org/stable/proc_macro/struct.Literal.html#method.byte_character)
- [`proc_macro::Literal::c_string`]
  (https://doc.rust-lang.org/stable/proc_macro/struct.Literal.html#method.c_string)

These APIs are now stable in const contexts:

- [`Atomic*::into_inner`]
  (https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicUsize.html#method.into_inner)
- [`io::Cursor::new`]
  (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.new)
- [`io::Cursor::get_ref`]
  (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.get_ref)
- [`io::Cursor::position`]
  (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.position)
- [`io::empty`]
  (https://doc.rust-lang.org/stable/std/io/fn.empty.html)
- [`io::repeat`]
  (https://doc.rust-lang.org/stable/std/io/fn.repeat.html)
- [`io::sink`]
  (https://doc.rust-lang.org/stable/std/io/fn.sink.html)
- [`panic::Location::caller`]
  (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.caller)
- [`panic::Location::file`]
  (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.file)
- [`panic::Location::line`]
  (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.line)
- [`panic::Location::column`]
  (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.column)

Cargo
-----

- [Prevent dashes in `lib.name`, always normalizing to `_`.]
  (rust-lang/cargo#12783)
- [Stabilize MSRV-aware version requirement selection in `cargo add`.]
  (rust-lang/cargo#13608)
- [Switch to using `gitoxide` by default for listing files.]
  (rust-lang/cargo#13696)

Rustdoc
-----

- [Always display stability version even if it's the same as the
  containing item.]
  (rust-lang/rust#118441)
- [Show a single search result for items with multiple paths.]
  (rust-lang/rust#119912)
- [Support typing `/` in docs to begin a search.]
  (rust-lang/rust#123355)

Misc
----

Compatibility Notes
-------------------

- [Update the minimum external LLVM to 17.]
  (rust-lang/rust#122649)
- [`RustcEncodable` and `RustcDecodable` are soft-destabilized, to
  be removed from the prelude in next edition.]
  (rust-lang/rust#116016)
- [The `wasm_c_abi` future-incompatibility lint will warn about use of the
  non-spec-compliant C ABI.]
  (rust-lang/rust#117918)
  Use `wasm-bindgen v0.2.88` to generate forward-compatible bindings.
- [Check return types of function types for well-formedness]
  (rust-lang/rust#115538)

Version 1.78.0 (2024-05-02)
===========================

Language
--------
- [Stabilize `#[cfg(target_abi = ...)]`]
  (rust-lang/rust#119590)
- [Stabilize the `#[diagnostic]` namespace and
  `#[diagnostic::on_unimplemented]` attribute]
  (rust-lang/rust#119888)
- [Make async-fn-in-trait implementable with concrete signatures]
  (rust-lang/rust#120103)
- [Make matching on NaN a hard error, and remove the rest of
  `illegal_floating_point_literal_pattern`]
  (rust-lang/rust#116284)
- [static mut: allow mutable reference to arbitrary types, not just
  slices and arrays]
  (rust-lang/rust#117614)
- [Extend `invalid_reference_casting` to include references casting
  to bigger memory layout]
  (rust-lang/rust#118983)
- [Add `non_contiguous_range_endpoints` lint for singleton gaps
  after exclusive ranges]
  (rust-lang/rust#118879)
- [Add `wasm_c_abi` lint for use of older wasm-bindgen versions]
  (rust-lang/rust#117918)
  This lint currently only works when using Cargo.
- [Update `indirect_structural_match` and `pointer_structural_match`
  lints to match RFC]
  (rust-lang/rust#120423)
- [Make non-`PartialEq`-typed consts as patterns a hard error]
  (rust-lang/rust#120805)
- [Split `refining_impl_trait` lint into `_reachable`, `_internal` variants]
  (rust-lang/rust#121720)
- [Remove unnecessary type inference when using associated types
  inside of higher ranked `where`-bounds]
  (rust-lang/rust#119849)
- [Weaken eager detection of cyclic types during type inference]
  (rust-lang/rust#119989)
- [`trait Trait: Auto {}`: allow upcasting from `dyn Trait` to `dyn Auto`]
  (rust-lang/rust#119338)

Compiler
--------

- [Made `INVALID_DOC_ATTRIBUTES` lint deny by default]
  (rust-lang/rust#111505)
- [Increase accuracy of redundant `use` checking]
  (rust-lang/rust#117772)
- [Suggest moving definition if non-found macro_rules! is defined later]
  (rust-lang/rust#121130)
- [Lower transmutes from int to pointer type as gep on null]
  (rust-lang/rust#121282)

Target changes:

- [Windows tier 1 targets now require at least Windows 10]
  (rust-lang/rust#115141)
 - [Enable CMPXCHG16B, SSE3, SAHF/LAHF and 128-bit Atomics in tier 1 Windows]
  (rust-lang/rust#120820)
- [Add `wasm32-wasip1` tier 2 (without host tools) target]
  (rust-lang/rust#120468)
- [Add `wasm32-wasip2` tier 3 target]
  (rust-lang/rust#119616)
- [Rename `wasm32-wasi-preview1-threads` to `wasm32-wasip1-threads`]
  (rust-lang/rust#122170)
- [Add `arm64ec-pc-windows-msvc` tier 3 target]
  (rust-lang/rust#119199)
- [Add `armv8r-none-eabihf` tier 3 target for the Cortex-R52]
  (rust-lang/rust#110482)
- [Add `loongarch64-unknown-linux-musl` tier 3 target]
  (rust-lang/rust#121832)

Refer to Rust's [platform support page][platform-support-doc]
for more information on Rust's tiered platform support.

Libraries
---------

- [Bump Unicode to version 15.1.0, regenerate tables]
  (rust-lang/rust#120777)
- [Make align_offset, align_to well-behaved in all cases]
  (rust-lang/rust#121201)
- [PartialEq, PartialOrd: document expectations for transitive chains]
  (rust-lang/rust#115386)
- [Optimize away poison guards when std is built with panic=abort]
  (rust-lang/rust#100603)
- [Replace pthread `RwLock` with custom implementation]
  (rust-lang/rust#110211)
- [Implement unwind safety for Condvar on all platforms]
  (rust-lang/rust#121768)
- [Add ASCII fast-path for `char::is_grapheme_extended`]
  (rust-lang/rust#121138)

Stabilized APIs
---------------

- [`impl Read for &Stdin`]
  (https://doc.rust-lang.org/stable/std/io/struct.Stdin.html#impl-Read-for-%26Stdin)
- [Accept non `'static` lifetimes for several `std::error::Error`
  related implementations] (rust-lang/rust#113833)
- [Make `impl<Fd: AsFd>` impl take `?Sized`]
  (rust-lang/rust#114655)
- [`impl From<TryReserveError> for io::Error`]
  (https://doc.rust-lang.org/stable/std/io/struct.Error.html#impl-From%3CTryReserveError%3E-for-Error)

These APIs are now stable in const contexts:

- [`Barrier::new()`]
  (https://doc.rust-lang.org/stable/std/sync/struct.Barrier.html#method.new)

Cargo
-----

- [Stabilize lockfile v4](rust-lang/cargo#12852)
- [Respect `rust-version` when generating lockfile]
  (rust-lang/cargo#12861)
- [Control `--charset` via auto-detecting config value]
  (rust-lang/cargo#13337)
- [Support `target.<triple>.rustdocflags` officially]
  (rust-lang/cargo#13197)
- [Stabilize global cache data tracking]
  (rust-lang/cargo#13492)

Misc
----

- [rustdoc: add `--test-builder-wrapper` arg to support wrappers
  such as RUSTC_WRAPPER when building doctests]
  (rust-lang/rust#114651)

Compatibility Notes
-------------------

- [Many unsafe precondition checks now run for user code with debug
  assertions enabled] (rust-lang/rust#120594)
  This change helps users catch undefined behavior in their code,
  though the details of how much is checked are generally not
  stable.
- [riscv only supports split_debuginfo=off for now]
  (rust-lang/rust#120518)
- [Consistently check bounds on hidden types of `impl Trait`]
  (rust-lang/rust#121679)
- [Change equality of higher ranked types to not rely on subtyping]
  (rust-lang/rust#118247)
- [When called, additionally check bounds on normalized function return type]
  (rust-lang/rust#118882)
- [Expand coverage for `arithmetic_overflow` lint]
  (rust-lang/rust#119432)

Internal Changes
----------------

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

- [Update to LLVM 18](rust-lang/rust#120055)
- [Build `rustc` with 1CGU on `x86_64-pc-windows-msvc`]
  (rust-lang/rust#112267)
- [Build `rustc` with 1CGU on `x86_64-apple-darwin`]
  (rust-lang/rust#112268)
- [Introduce `run-make` V2 infrastructure, a `run_make_support`
  library and port over 2 tests as example]
  (rust-lang/rust#113026)
- [Windows: Implement condvar, mutex and rwlock using futex]
  (rust-lang/rust#121956)


Version 1.77.0 (2024-03-21)
==========================

- [Reveal opaque types within the defining body for exhaustiveness checking.]
  (rust-lang/rust#116821)
- [Stabilize C-string literals.]
  (rust-lang/rust#117472)
- [Stabilize THIR unsafeck.]
  (rust-lang/rust#117673)
- [Add lint `static_mut_refs` to warn on references to mutable statics.]
  (rust-lang/rust#117556)
- [Support async recursive calls (as long as they have indirection).]
  (rust-lang/rust#117703)
- [Undeprecate lint `unstable_features` and make use of it in the compiler.]
  (rust-lang/rust#118639)
- [Make inductive cycles in coherence ambiguous always.]
  (rust-lang/rust#118649)
- [Get rid of type-driven traversal in const-eval interning]
  (rust-lang/rust#119044),
  only as a [future compatiblity lint]
  (rust-lang/rust#122204) for now.
- [Deny braced macro invocations in let-else.]
  (rust-lang/rust#119062)

Compiler
--------

- [Include lint `soft_unstable` in future breakage reports.]
  (rust-lang/rust#116274)
- [Make `i128` and `u128` 16-byte aligned on x86-based targets.]
  (rust-lang/rust#116672)
- [Use `--verbose` in diagnostic output.]
  (rust-lang/rust#119129)
- [Improve spacing between printed tokens.]
  (rust-lang/rust#120227)
- [Merge the `unused_tuple_struct_fields` lint into `dead_code`.]
  (rust-lang/rust#118297)
- [Error on incorrect implied bounds in well-formedness check]
  (rust-lang/rust#118553),
  with a temporary exception for Bevy.
- [Fix coverage instrumentation/reports for non-ASCII source code.]
  (rust-lang/rust#119033)
- [Fix `fn`/`const` items implied bounds and well-formedness check.]
  (rust-lang/rust#120019)
- [Promote `riscv32{im|imafc}-unknown-none-elf` targets to tier 2.]
  (rust-lang/rust#118704)
- Add several new tier 3 targets:
  - [`aarch64-unknown-illumos`]
    (rust-lang/rust#112936)
  - [`hexagon-unknown-none-elf`]
    (rust-lang/rust#117601)
  - [`riscv32imafc-esp-espidf`]
    (rust-lang/rust#119738)
  - [`riscv32im-risc0-zkvm-elf`]
    (rust-lang/rust#117958)

Refer to Rust's [platform support page][platform-support-doc]
for more information on Rust's tiered platform support.

Libraries
---------

- [Implement `From<&[T; N]>` for `Cow<[T]>`.]
  (rust-lang/rust#113489)
- [Remove special-case handling of `vec.split_off
  (0)`.](rust-lang/rust#119917)

Stabilized APIs
---------------

- [`array::each_ref`]
  (https://doc.rust-lang.org/stable/std/primitive.array.html#method.each_ref)
- [`array::each_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.array.html#method.each_mut)
- [`core::net`]
  (https://doc.rust-lang.org/stable/core/net/index.html)
- [`f32::round_ties_even`]
  (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.round_ties_even)
- [`f64::round_ties_even`]
  (https://doc.rust-lang.org/stable/std/primitive.f64.html#method.round_ties_even)
- [`mem::offset_of!`]
  (https://doc.rust-lang.org/stable/std/mem/macro.offset_of.html)
- [`slice::first_chunk`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first_chunk)
- [`slice::first_chunk_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first_chunk_mut)
- [`slice::split_first_chunk`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first_chunk)
- [`slice::split_first_chunk_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first_chunk_mut)
- [`slice::last_chunk`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last_chunk)
- [`slice::last_chunk_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last_chunk_mut)
- [`slice::split_last_chunk`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last_chunk)
- [`slice::split_last_chunk_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last_chunk_mut)
- [`slice::chunk_by`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.chunk_by)
- [`slice::chunk_by_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.chunk_by_mut)
- [`Bound::map`]
  (https://doc.rust-lang.org/stable/std/ops/enum.Bound.html#method.map)
- [`File::create_new`]
  (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.create_new)
- [`Mutex::clear_poison`]
  (https://doc.rust-lang.org/stable/std/sync/struct.Mutex.html#method.clear_poison)
- [`RwLock::clear_poison`]
  (https://doc.rust-lang.org/stable/std/sync/struct.RwLock.html#method.clear_poison)

Cargo
-----

- [Extend the build directive syntax with `cargo::`.]
  (rust-lang/cargo#12201)
- [Stabilize metadata `id` format as `PackageIDSpec`.]
  (rust-lang/cargo#12914)
- [Pull out as `cargo-util-schemas` as a crate.]
  (rust-lang/cargo#13178)
- [Strip all debuginfo when debuginfo is not requested.]
  (rust-lang/cargo#13257)
- [Inherit jobserver from env for all kinds of runners.]
  (rust-lang/cargo#12776)
- [Deprecate rustc plugin support in cargo.]
  (rust-lang/cargo#13248)

Rustdoc
-----

- [Allows links in markdown headings.]
  (rust-lang/rust#117662)
- [Search for tuples and unit by type with `()`.]
  (rust-lang/rust#118194)
- [Clean up the source sidebar's hide button.]
  (rust-lang/rust#119066)
- [Prevent JS injection from `localStorage`.]
  (rust-lang/rust#120250)

Misc
----

- [Recommend version-sorting for all sorting in style guide.]
  (rust-lang/rust#115046)

Internal Changes
----------------

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

- [Add more weirdness to `weird-exprs.rs`.]
  (rust-lang/rust#119028)
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